<!DOCTYPE html>
<html>
<head lang="en">
    <meta charset="UTF-8">
    <title></title>
    <style>

        html, body {
            background: red;
            margin: 0;
            padding: 0;
        }
        .valid {
            margin-top: 350px;
            height: 350px;
            background: green;
            display: block;
            margin-bottom: 500px;
        }
    </style>
</head>
<body><div class="valid">&nbsp;</div></body>
</html>
